1. Technical Field
The present invention relates to metallurgical processes and apparatus, and more particularly to metallurgical processes and apparatus in which metal chips are melted in a molten metal vortex which is fed by an inert gas bubble-actuated molten metal pump.
2. Technical Background
My following U.S. patents disclose various apparatus and processes related to the introduction of metal chips into the charge-well of a metal melting furnace and the conveyance of molten metal from one place to another within or out of a metal melting furnace.
U.S. Pat. No. 4,710,126 discloses a process for producing dry metal chips. This process includes the steps of entraining fluid-containing metal chips in a gas, introducing the gas into a cyclone separator having an internal wall heated to fluid-vaporizing temperature by combustion in a surrounding chamber, purging and vaporizing fluid from said chips, exhausting hot gases and exiting dried metal chips from said separator, conducting hot gaseous products of combustion from the combustion chamber to a continuous centrifuge, extracting extractable fluid from starting metal chips in the centrifuge, entraining the chips in the hot gaseous products of combustion introduced into the centrifuge, and conducting the gaseous products with entrained chips from the continuous centrifuge to the cyclone separator, thereby providing an essentially closed system. The combustion chamber may be a part of an afterburner furnace and hot gases entraining vaporized oil exhausted from the cyclone separator may be recycled and employed as fuel for the combustion chamber.
U.S. Pat. No. 4,721,457 discloses a process for producing dried and cleaned metal chips by entraining metal chips in a gas, introducing the gas into a cyclone separator having a wall heated to fluid-vaporizing temperature by combustion effected in a surrounding chamber, purging fluid from said chips, exhausting hot gases and exiting dried metal chips from said separator, conducting hot gaseous products of combustion from the combustion chamber to a continuous centrifuge, extracting extractable fluid from starting metal chips, which may be previously uncleaned and/or unwashed, in the centrifuge, entraining the chips in the hot gaseous products of combustion introduced into the centrifuge, and conducting the gaseous products with entrained chips from the continuous centrifuge to the cyclone separator, thereby providing an essentially closed system. The combustion chamber may be a part of an afterburner furnace and hot gases entraining vaporized oil exhausted from the cyclone separator may be recycled and employed as fuel for the combustion chamber. Provision is made in the system for hot water and/or steam from either an external source of from a water jacket around the cyclone separator, preferably together with solvent and/or detergent, and a final chip drying step wherein the drying is effected using products of combustion which are en route back to the continuous centrifuge.
U.S. Pat. No. 4,872,907 discloses an apparatus and method for charging metal chips into a molten bath of the metal from which the chips are formed, comprising a compacting extruded and a delivery conduit which is resistant to the mass of molten metal and which is pivotable to dip into the molten metal bath when chips are being charged thereinto and out of contact with the bath when charging is to be discontinued, are disclosed. The chips are forced through the delivery conduit in the form of a compacted or densified mass preferably having a density between about 30 and 60 percent of the density of the solid metal and preferably between about 55 and 80 pounds per cubic foot. Feed is continued while the delivery conduit is in the molten metal bath and until it is removed therefrom to prevent entry of molten metal into the delivery conduit. The method is preferably conducted on a continuous basis and various sensors with appropriate wiring may be employed for safety and for making the method substantially automatic in operation.
U.S. Pat. No. 5,203,910 discloses a method for the conveyance of molten metal from one place to another, in a high-temperature molten metal pool in a metal-melting furnace or out of said molten metal pool, employing an at least partially-inclined elongated conveying conduit and gas feed means for feeding inert gas into the lower end of the conveying conduit and thereby inducing a flow of molten metal in and through said conveying conduit, is disclosed, along with suitable apparatus for carrying out the said method wherein the parts or elements coming into contact with the high-temperature molten metal pool are of a suitable refractory material.
U.S. Pat. No. 5,211,744 discloses a process for utilization of metal chips, especially scrap metal chips, particularly brass and aluminum, by introduction of the metal chips into a pool of molten metal of which they are formed or an alloy thereof. The process allows for minimization of fuel cost, heat loss, and minimal conversion of the metal at the surface of the molten metal pool to metal oxide, as well as an increase in the yield of utilizable metal from the remelting or recycling operation, by maintaining a non-oxidizing atmosphere at the surface of the molten metal pool and optionally utilizing vaporized residual impurities from chips being recycled such as oil, lacquer, or similar vaporizable impurity to assist in maintaining the non-oxidizing atmosphere. Elimination of impurity-removal steps previously required for preparation of the chips for recycling by introduction into such a molten metal pool is eliminated. Environmental pollution is also conveniently and simultaneously substantially reduced from vaporizable contaminants, fumes, and decomposition products of combustion thereof.
U.S. Pat. No. 5,395,424 discloses a method for the conveyance of molten metal from one place to another, in a high-temperature molten metal pool in a metal-melting furnace or out of said molten metal pool employing at least a partially-inclined elongated conveying conduit and gas feed means for feeding inert gas into the lower end of the conveying conduit is employed. A flow of molten metal in and through said conveying conduit, is disclosed, along with suitable apparatus for carrying out the said method wherein the parts or elements coming into contact with the high-temperature molten metal pool are of a suitable refractory material. According to the present invention, an intermittent or pulsating inert gas feed is employed to produce essentially spherical or cylindrical bubbles within the conveying conduit, thereby resulting in greater efficiency and economy because of the possibility of reducing the quantity of inert gas employed to induce the flow of an identical amount of molten metal.
U.S. Pat. No. 5,407,462 discloses a mass flow gravity feed furnace charger comprises a vertically-oriented elongated hollow conduit which is associated with an apertured heat-resistant charge-well cover adapted to lie essentially in contact with the upper surface of a molten metal pool in the charge well of a metal-melting furnace. Presized scrap metal charged into the conduit collects atop the surface of the molten metal pool, since the bottom opening of the conduit communicates with the charge-well cover aperture and permits the metal scrap to fall by gravity directly into the molten metal in the charge well. When the weight of the metal scrap column is sufficient to offset the resistance of the upper surface of the molten metal pool, the weight of the collected metal scrap gravitationally forces it into the molten metal mass it melts and is assimilated. Employment of the method and charge of the invention enables the controlled introduction of metal scrap by mass flow and gravity feed directly into and beneath the surface of the pool of molten metal and obviates numerous disadvantages and inconveniences of past practices.
U.S. Pat. No. 5,468,280 discloses a method for the conveyance of molten metal from one place to another in a high-temperature molten metal pool in a metal-melting furnace or out of said molten metal pool. At least partially-inclined elongated conveying conduit and gas feed means for feeding inert gas into the lower end of the conveying conduit is employed. A flow of molten metal is thereby inducted in and through said conveying conduit, is disclosed, along with suitable apparatus for carrying out the said method wherein the parts or elements coming into contact with the high-temperature molten metal pool are of a suitable refractory material. The inert gas is fed into the conveying conduit at a supersonic velocity, thereby simultaneously effecting a degassing of the molten metal while it is being conveyed.
U.S. Pat. No. 5,735,935 discloses an inert gas bubble-actuated molten metal pump which is located in a metal-melting furnace to effect circulation of molten metal throughout the furnace. The inert gas employed to actuate the molten metal pump is captured beneath a heat-resistant and flame-resistant cover located above the exit port of the pump and over a substantial portion of the molten metal to thereby to prevent splashing, spattering and disruption of a thin protective layer or skin of oxidized metal at the surface of the molten metal as well as to provide a non-oxidizing atmosphere at the surface of the molten metal beneath said cover. In this manner the inert gas is employed efficiently and economically.
U.S. Pat. No. 5,853,454 discloses a mass flow gravity feed furnace charger apparatus includes a charge-well cover having an aperture and an essentially vertical conduit for forming a substantially vertically-oriented column of metal chips or scrap within and above the aperture, and structure for bringing both the cover and conduit into position above a charge-well. The conduit is rapidly movable up and down to force the metal chips or scrap into molten metal in the charge-well even when the dross level at the surface of the molten metal is considerable, so that the apparatus and corresponding methods permit charging when gravity feed alone is not sufficient or sufficiently rapid. In a preferred embodiment, the conduit has an interior surface provided with gripping means to assist with the downward movement of metal chips or scrap into the molten metal in the charge well when the up and down motion of the conduit is in effect.
U.S. Pat. No. 5,919,283 discloses an inert gas bubble-actuated molten metal pump is located between one section of a metal-melting furnace and a second section to pump molten metal form the one section, wherein the molten metal is at a higher temperature, into the second section, wherein the molten metal is at a lower temperature, and its effluent is directed into contact with metal chips being charged into the second section, thereby assisting in the more rapid melting of the chips into the molten metal mass in the second section. The inert gas employed to acturate the molten metal pump is captured beneath a heat-resistant and flame-resistant cover located above the exit port of the pump and over a substantial portion of the molten metal mass in the second section, thereby providing a non-oxidizing atmosphere at the surface of the molten metal mass or pool beneath said cover. In this manner the inert gas is employed not only to actuate the inert gas bubble-actuated molten metal pump, but also to assist in the rapid melting of metal chips being charged, as well as to provide a non-oxidizing atmosphere at the surface of the molten metal.
U.S. Pat. No. 5,984,999 discloses an arrangement in which the vortex well of a metal melting furnace is provided with an internal cavity having a circular cross section when viewed from the top, preferably a cavity of cylindrical or conical configuration, and with a peripheral exit port located tangentially with respect to said cavity at a lower level thereof for exit of molten metal into the main chamber of the furnace. An inert gas bubble-actuated molten metal pump brings molten metal from a hotter section of the furnace, advantageously directly form the main chamber, and has its exit port located tangentially to the periphery of the cavity at an upper level thereof, thereby creating vortical flow of molten metal therein and for circulation of hotter molten metal throughout the furnace. A head of molten metal can be created in the vortex well, which advantageously has an exit port of restricted internal cross-sectional area, to assist with attainment of these objective. A heat and flame-resistant cover may be located above the cavity and advantageously has an aperture therein for the loading of metal chips or scrap thereinto. A gravity-feed chip charger may surmount the aperture for the discharge of new metal chips or scrap into the cavity through the said aperture.
U.S. Pat. No. 6,068,812 discloses an inert gas bubble-actuated molten metal pump, for the movement of molten metal in a molten-metal bath, which obviates the necessity of a heat proof and flameproof cover to counteract splashing and spattering at the surface of the molten metal bath above the pump, comprising an inert gas diffusion means at an upper end thereof, the diffusion means having an upper surface containing a multiplicity of small upwardly-opening apertures for the breaking up of large bubbles and the diffusion of small bubbles of inert gas upwardly therethrough. The pump includes a refractory block which comprises a conveying conduit which is preferably elongated in width and a spreader cavity in communication with both a passageway in the block for providing a source of inert gas and a lower end of the conveying conduit.
My above referenced patents are incorporated herein by reference.
The purpose for creating a vortex in the vortex well is to rapidly submerge the small particles of metal whose mass would otherwise prevent the particles from penetrating the surface tension of the molten metal bath, thus causing a substantial increase in the percentage of metal loss due to oxidation. It has, however, has been determined that further steps must be taken to reduce oxidation, particularly when relatively more expensive metals such as aluminum are being used.